Solution to Service Lane Problem on HackerRank


The problem:

Calvin is driving his favorite vehicle on the 101 freeway. He notices that the check engine light of his vehicle is on, and he wants to service it immediately to avoid any risks. Luckily, a service lane runs parallel to the highway. The length of the highway and the service lane is N units. The service lane consists of N segments of unit length, where each segment can have different widths.

Calvin can enter into and exit from any segment. Let’s call the entry segment as index i and the exit segment as index j. Assume that the exit segment lies after the entry segment(j>i) and i ≥ 0. Calvin has to pass through all segments from index i to indexj (both inclusive).

Calvin has three types of vehicles – bike, car and truck, represented by 1, 2 and 3 respectively. These numbers also denote the width of the vehicle. We are given an array width[] of length N, where width[k] represents the width of kth segment of our service lane. It is guaranteed that while servicing he can pass through at most 1000 segments, including entry and exit segments.

If width[k] is 1, only the bike can pass through kth segment.

If width[k] is 2, the bike and car can pass through kth segment.

If width[k] is 3, any of the bike, car or truck can pass through kth segment.

Given the entry and exit point of Calvin’s vehicle in the service lane, output the type of largest vehicle which can pass through the service lane (including the entry & exit segment)

Input Format
The first line of input contains two integers – N & T, where N is the length of the freeway, and T is the number of test cases. The next line has N space separated integers which represents the width array.

T test cases follow. Each test case contains two integers – i & j, where i is the index of segment through which Calvin enters the service lane and j is the index of the lane segment where he exits.

Output Format
For each test case, print the number that represents the largest vehicle type that can pass through the service lane.

Solution in Common Lisp

(defun even (x) (= (rem x 2) 0))

(defun processArray (widths len) (if (> len 0)
        (progn
          (setq pos (+ pos 1))
          (setq pos (position #\space widths :start pos))
          (setq value (parse-integer widths :start startPos :end pos))
          (setq widthsArr (append widthsArr (list value)))
          (setq startPos pos)
          (processArray widths (- len 1))
        ))) 

(defun traverseArray (startIndex endIndex smallest) (if (<= startIndex endIndex)
            (progn 
              (if (= (nth startIndex widthsArr) 1)
                1)
              (if (< (nth startIndex widthsArr) smallest)
                (setq smallest (nth startIndex widthsArr)))
              (traverseArray (+ startIndex 1) endIndex smallest))
            smallest))

(defun main (cases) (if (> cases 0)
      (progn 
        (setq line (read-line))
        (setq pos (position #\space line))
        (setq startIndex (parse-integer line :end pos))
        (setq endIndex (parse-integer line :start pos))

        (format t "~d~%" (traverseArray startIndex endIndex 10))        
        
        (main (- cases 1))
      )))

(setq line (read-line))
(setq pos (position #\space line))

(setq len (parse-integer line :end pos))
(setq cases (parse-integer line :start pos))

(setq widths (read-line))
(setq widthsArr ())

(setq pos 0)
(setq startPos 0)
(processArray widths len)

(main cases)

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